Electrosurgical instruments have been used for many years in high-frequency surgery especially in order to coagulate biological tissue as well as to cut it. For coagulation a high-frequency current is passed through the tissue to be treated, so that it changes due to protein coagulation and dehydration. The tissue contracts in such a way that the vessels are closed and bleeding is staunched. After coagulation has taken effect the tissue can for example be separated by means of a mechanically operating cutting instrument.
Electrosurgical processes can be carried out in a monopolar as well as a bipolar way. With monopolar technology the electrosurgical instrument has only one current supply and the tissue to be treated (or the patient) must therefore be placed at the other potential. Bipolar instruments which are constructed with two separately isolated sections are gaining more and more in significance, however. The current path between the electrode parts can thus be calculated and does not run long distances through the body of the patient. The effect of for example pacemakers or other equipment which are connected to the patient during an operation is thus reduced.
Bipolar coagulation instruments comprise essentially two limbs that have an articulated connection at whose proximal ends handle devices are provided for handling the limbs. At the distal ends of the limbs are electrode parts with coagulation surfaces for gripping the tissue and for passing the coagulation current through the tissue. For this the HF current supplied by the HF generator is fed via the current supply devices to the electrode parts of the bipolar instrument.
The problem with conventional electrosurgical instruments, however, is that the tissue once gripped between electrode parts easily slides away or slips. This can lead to complications in particular when the operating area is difficult to see by the surgeon, for example with endoscopic procedures or with heavily bleeding sections of tissue and restoring a grip on the tissue is difficult.
Commercially available instruments are frequently manufactured with structured electro-parts that is to say with structured coagulation surfaces, so that the tissue is gripped securely between the coagulation surfaces of the electrode parts. The electrode parts comprise for example wave-shaped coagulation surfaces.
Structuring of coagulation surfaces is, however, involves many disadvantages. Even the manufacture of such coagulation surfaces is very expensive. In addition structuring promotes adherence of the tissue to the surfaces during the procedure, so that preparation for reuse is also very time-consuming. The complicated geometry also makes reconditioning of the coagulation surface difficult.